线型离子阱中空间电荷效应的理论分析

线型离子阱中的离子在射频场作用下做宏观的久期运动,久期运动频率与实验参数有关.但当离子阱中囚禁大量同种电荷的离子时,空间电荷效应会导致离子间存在相互排斥的库仑力,使离子的运动频率发生漂移.本文通过求解泊松方程计算了空间电荷产生的附加电场的解析表达式,在小振动近似下理论计算了该附加电场对久期运动频率的影响,模拟了不同离子云中心密度下久期频率的漂移,讨论了离子云的数目、温度与实验参数之间的关系.对用离子阱进行的频标实验、碰撞实验和其他方面的研究都具有重要的指导意义.     

控制离子云混沌运动中的不稳定性

射频阱中离子云与检测场的相互作用由Dufing方程描述．在小阻尼条件下，得到嵌于混沌吸引子中的不稳定周期解及其稳定性条件．分析表明，调节直流扫描电压等参数去拟合该条件，可以控制混沌运动中的不稳定性．有关实验定性支持这一结论． 关键词：     

Paul阱中离子云囚禁时间的分析

结合缓冲气体Ｈｅ对囚禁离子云Ｎ＾＋２的冷却实验结果，给出了在综合考虑射频加热和缓冲气体冷却效应情形下，阱中囚禁离子数随时间变化的理论模型。讨论了Ｐａｕｌ阱中的加热数，γ，离子云温度Ｔ，随机为力涨落Ｄ等参数对囚禁时间的影响。     

中性粒子在Ioffe阱中的经典运动方程的Floquet解

研究中性粒子在Ioffe阱中近原点区域的囚禁时,阱中的磁场可以呈现出一种简明的形式.磁矩μ反平行于磁场的中性粒子在阱中与磁场发生相互作用,借助相互作用势,可以获得粒子在阱中的经典运动方程.在一定的条件下,采用迭代近似的目的,将方程演化为马丢方程的形式,利用传统的WKBJ目的可实现方程的近似求解.研究阱中中性粒子的囚禁问题时,感兴趣的是马丢方程的Floquet解,即周期为π,2π的全周期和半周期解,欲获得这种周期解,马丢方程中的参数λ和q必须满足一定的关系,为此必须选择阱的特定参数和粒子的特定初始条件,对这一问题进行了探索性的研究.     

Paul阱中共面两离子系统的能量本征态

通过对Paul阱中共面两离子体系的研究，考虑共面两离子在Paul阱中库仑关联，得到了两离子系统Schrdinger方程的精确解；椐方程的精确解，分析了质心能级简并情况，计算了两离子的平衡距离和低能级的几个态函数，设计程序作出了质心径向概率分布图. 关键词： Paul阱 两离子 共面 量子逻辑操作     

周期耦合量子阱中的输运问题

采用Gurvitz等人直接求解薛定谔方程的方法并结合数值计算,分析了驱动频率对周期耦合量子阱体系的电流的影响.结果表明：当驱动频率小于耦合量子阱间的能级差时,随着驱动频率的增大,系统平衡时的电流增加,当驱动频率大于耦合量子阱间能级差时,随着驱动频率的增大,平衡时的电流减小.这样,通过控制外场驱动频率来达到控制电流的目的. 关键词： 量子阱 驱动频率 电流     

囚禁单离子的量子阻尼运动

用包含偶极和四极虚势能项的非厄米哈密顿算符来描述Paul阱中囚禁阻尼单离子在静电场下的量子运动.通过导出和分析系统的精确解,得到在PT对称和不对称情形下的不同实能谱与稳定量子态,以及PT不对称情形的虚能谱和衰减量子态,同时给出相应于不同态的参数区域和存活概率.结果发现该非厄米系统外场参数能惟一确定量子稳定态并导致波函数形态变化,据此提出非相干操控相应量子跃迁的方法.让量子态衰减导致的离子位置期待值的衰减与经典阻尼谐振子的衰减一致,得到虚势能参数与经典阻尼参数的对应关系.所得结果将进一步丰富具有广泛应用背景的囚禁离子动力学.     

幺正极限附近费米气体反常激发模式的涡旋

在幺正极限附近研究了处于旋转外势中费米气体的量子化涡旋动力学. 选取适当的试探波函数并利用含时变分法, 得到了小振幅涡旋运动方程及描述其反常激发模式的解. 详细讨论了在幺正极限附近的反常模式产生的条件. 结果显示系统囚禁外势的临界转动频率在幺正极限附近随粒子间相互作用参数的增加而变大, 而涡旋进动的周期则随着粒子间相互作用参数的增加而减小. 关键词： 费米气体 涡旋 幺正极限     

基础水平运动的弹簧摆的周期解与稳定性

针对基础水平运动的弹簧摆的非线性动力学响应进行研究,利用拉格朗日方程建立了系统的动力学方程.将离散傅里叶变换、谐波平衡法以及同伦延拓方法相结合,对系统的周期响应进行求解,避免了传统方法计算中使用泰勒展开引起的小振幅的限制,与数值计算结果的对比表明该求解方法具有较高的精确度.利用Floquet理论分析了周期响应的稳定性,给出了基础运动振幅和频率对系统周期响应的影响.研究发现:对应某些基础频率和振幅,系统的周期响应可能发生Hopf分岔;利用数值计算研究了Hopf分岔后系统响应随基础频率和振幅的变化,发现系统出现了倍周期运动、拟周期运动和混沌等复杂的动力学行为.研究表明系统进入混沌的主要路径是拟周期环面破裂和阵发性.     

激光脉冲作用下囚禁离子的规则与混沌运动

研究驻波型激光脉冲作用下，失谐量足够大时，囚禁于Paul阱中的单离子系统的久期运动.通过分析和数值计算相结合的方法，导出系统的精确解及其描述的时间演化性质，得到系统的规则和混沌运动轨道以及阱频很小时系统进入整体混沌的临界条件,并提出了控制系统共振失稳的方法. 关键词： 激光脉冲 囚禁离子 规则与混沌运动 精确解 稳定性     

Paul阱中离子运动及稳定性分析

Paul离子阱由于没有外加磁场所引起的塞曼效应的影响,已成为离子存储及研究离子的重要装置.根据在实验中所采用的Paul离子阱结构及电场分布特点,列出阱内离子运动方程并进行求解,对其中各种运动进行分析,同时还分析了离子存储稳定性.最后对所作的研究进行总结,得到如下结论:阱中离子的运动为谐振运动、基频微运动和高阶微振动.     

Determination of the geometric parameters κz and κr of a linear Paul trap

An effective method for determining the geometric parameters of a linear Paul trap is provided and carried out in this paper. The method is based on exciting the secular motion of laser-cooled Ca⁺ ions in a linear Paul trap with varied trapping potentials. Taking advantage of the segmented structure of the linear Paul trap, both the axial and the radial geometric parameters are obtained by applying external excitation fields to the trapping electrodes directly. The axial geometric parameter of our linear Paul trap is determined to be 0.374(3), and, for the first time, the radial geometric parameter is determined to be 0.928(2).     

Surface-electrode Paul trap with optimized near-field microwave control

We describe the design of a microfabricated Paul trap with integrated microwave conductors for quantum simulation and entangling logic gates. We focus on an approach where near-field amplitude gradients of microwave fields from conductors in the trap structure induce the required spin-motional couplings. This necessitates a strong amplitude gradient of the microwave near-field at the position of the ions, while the field itself needs to be suppressed as much as possible. We introduce a single meander-like microwave conductor structure which provides the desired field configuration. We optimize its parameters through full-wave microwave numerical simulations of the near-fields. The microwave conductor is integrated with additional dc and rf electrodes to form the actual Paul trap. We discuss the influence of the additional electrodes on the field configuration. To be able to fine-tune the overlap of the Paul trap rf null with the microwave field minimum, our trap design allows relative tuning of trap rf electrode amplitudes. Our optimized geometry could achieve a ratio of sideband-to-carrier excitations comparable to experiments with focused laser beams.     

Frequency dependence of the amplitude of domain-wall oscillations in an acoustic wave field

The velocity of oscillatory motion of domain walls is investigated as a function of the parameters of a magnetic material and an external acoustic field. The dependence of the amplitude of domain-wall oscillations on the frequency of an external acoustic wave is determined. It is found that this dependence exhibits a resonant behavior.     

Measurement of Secular Motion Frequency in Miniature Paul Trap to Ascertain the Stability Parameters

40Ca＋ ions are trapped and laser cooled in a miniature Paul trap. The secular motion was observed by the radio-frequency resonance of the ion cloud and Zeeman profile sidebands of a single ion experimentally. The trap stability parameters a and q are determined with an uncertainty under 1% by the secular motion frequency measurement. The trap efficiency is 0.75. A practicable suggestion is given for the benefits of a new trap design.     

Plasma coating of nanoparticles in the presence of an external electric field

Film deposition onto nanoparticles by low-pressure plasma in the presence of an external electric field is studied numerically. The plasma discharge fluid model along with surface deposition and heating models for nanoparticles, as well as a dynamics model considering the motion of nanoparticles, are employed for this study. The results of the simulation show that applying external field during the process increases the uniformity of the film deposited onto nanoparticles and leads to that nanoparticles grow in a spherical shape. Increase in film uniformity and particles sphericity is related to particle dynamics that is controlled by parameters of the external field like frequency and amplitude. The results of this work can be helpful to produce spherical core-shell nanoparticles in nanomaterial industry.     

Stability of an aqueous quadrupole micro-trap

The recently demonstrated functionality of an aqueous quadrupole micro- or nano-trap opens a new avenue for applications of Paul traps, like confinement of a charged biomolecule which requires a water environment for its chemical stability. Besides the strong viscosity forces, the motion of a charged particle in the aqueous trap is subject to dielectrophoretic and electrophoretic forces. In this study, we describe the general conditions for stability of a charged particle in an aqueous quadrupole trap. We find that for typical micro-trap parameters, the effects of both dielectrophoresis and electrophoresis significantly influence the trap stability. In particular, an aqueous quadrupole trap could play the role of a synthetic virtual nanopore for the third generation of DNA sequencing technology.     

Surface Planar Ion Chip for Linear Radio-Frequency Paul Traps

We propose a surface planar ion chip which forms a linear radio frequency Paul ion trap. The electrodes reside in the two planes of a chip, and the trap axis is located above the chip surface. Its electric field and potential distribution are similar to the standard linear radio frequency Paul ion trap. This ion trap geometry may be greatly meaningful for quantum information processing.     

Laser controlled quantum motion of two Paul trapped ions

We investigate the quantum motion of two ions stored in a Paul trap and interacting with a time-periodic laser field. In the pseudopotential approximation and large detuning condition, we find that the relative motion is independent of the laser field, but the exact centre-of-mass motion is closely related to the laser field. By adjusting the laser intensity and frequency, we can well control the quantum motion of the centre-of-mass. We illustrate some physical properties described by the centre-of-mass states, such as the squeezed coherent property, the widths and heights of the wavepackets of probability density, the classical-quantum correspondence, the resonance ladders of expectation energy and the transition probabilities between time-dependent quantum levels.